As a semiconductor device intended to be downsized, a small semiconductor package slightly larger in size than a semiconductor chip, which is called a QFN (Quad Flat Non-leaded Package), has been developed and the semiconductor package, having such a structure that a plurality of leads to be external terminals are disposed on a peripheral portion of a rear face of a sealing portion formed by a resin mold, is called a peripheral type.
In the QFN, since the respective leads are exposed to the rear face of the sealing portion, bonding regions between the respective leads and a sealing resin are very small, so that various devices for increasing a bonding strength between each lead and the sealing portion have been made.
Note that the structure of the QFN is described in, for example, “Monthly Semiconductor World Special Edition '99, Semiconductor Assembly/Inspection Technology”, pp. 53-57, published by Kabushiki Kaisha Press Journal, on Jul. 27, 1998.
In the QFN, as shown in a comparative example of FIG. 14, the extending length (P) of a mounted surface 1d, which is exposed to a rear surface 3a of a sealing portion 3 of each lead 1a and functions as an external terminal, has the relation “Q≧P” in comparison with the length (Q) of a sealing-portion forming surface 1g that is located on an opposite side thereof and covered with a resin sealing portion.
This is because, on a sealing-portion forming surface 1g of each lead 1a, there are formed a plurality of concave portions 1m, which prevents exertion of a stress to a wire bonding portion at a time of cutting the lead and increases a pulling strength of each lead with respect to a horizontal direction, whereby the length (Q) of the sealing-portion forming surface 1g is larger and consequently the relation “Q≧P” is formed.
When it is intended to mount a larger semiconductor chip without changing the package size in accordance with demands etc. from a customer under the above condition, the extending length (P) of the mounted surface 1d cannot be shortened in view of the fixed package size since the length (P) is defined per package size based on EIJA standards (Standards of Electronic Industries Association of Japan).
Accordingly, it becomes a problem that mounting of the larger semiconductor chip cannot be achieved without changing the package size.
An object of the present invention is to provide a semiconductor device in which mountable chip size is increased and to provide a manufacturing method thereof.
The above and other objects and novel features of the present invention will become apparent from a description of the specification and the accompanying drawings.